1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device and manufacturing method thereof.
2. Description of the Related Art
Conventionally, a titanium film (Ti film) has been used in a portion of a contact conductive plug to make contact with a semiconductor substrate (for example, a silicon substrate) and an aluminum conductive layer (aluminum film), in order to reduce the contact resistance of the semiconductor substrate and the aluminum conductive layer with the contact conductive plug.
In addition, a titanium nitride film (TiN film) is used in the contact conductive plug as one of the constituent elements thereof, in order to stabilize the film-forming reaction of a tungsten film composing the contact conductive plug and ensure the adhesiveness of the tungsten film to a foundation insulating layer.
Since a WF6 gas used when the tungsten film is formed reacts with titanium (Ti), silicon (Si) or aluminum (Al) to cause film delamination, these materials need to be covered and protected with a titanium nitride film (TiN film).
JP2001-168057A discloses a semiconductor device manufacturing method in which the delamination of a barrier metal film is suppressed when a tungsten film is buried in a contact hole through a barrier metal. In this method, a titanium film is sputter-formed on an upper surface of a substrate including a contact hole. Then, a first titanium nitride film is sputter-formed on the titanium film in a nitrogen atmosphere, while heating the substrate with a high-temperature Ar gas. Next, a second titanium nitride film is sputter-formed in a 100% nitrogen atmosphere, so as to cover the first titanium nitride film. Thereafter, the contact hole is filled with the tungsten film through a barrier metal film composed of a laminated film including the titanium film, the first titanium nitride film, and the second titanium nitride film.
JP11-87272A discloses a manufacturing method in which a high-quality tungsten film can be formed on a TiN film. In this method, a silicon oxide film is formed on a silicon substrate. Then, the silicon oxide film is patterned into a contact hole shape to fabricate a base substrate. Next, a 30 nm-thick
Ti film is formed on exposed portions of the silicon substrate and on the silicon oxide film by a sputtering deposition method. Subsequently, a 60-second nitrogen plasma treatment is performed under the temperature, pressure and power conditions of 400° C., 1 Torr and 300 W, respectively, to nitride a surface of the Ti film. Then, a 50 nm-thick TiN film is formed by a sputtering deposition method. Thereafter, a 350 nm-thick tungsten film is formed on the TiN film by a CVD method.
JP11-87272A discloses another method for forming a tungsten film. In this method, an 800 nm-thick Al film is formed first by a sputtering deposition method, and then a 30 nm-thick Ti film (titanium film) is formed on the Al film by a sputtering deposition method. Subsequently, a 60-second nitrogen plasma treatment is performed under the temperature, pressure and power conditions of 400° C., 1 Torr and 300 W, respectively, to nitride a surface of the Ti film. Then, a 100 nm-thick TiN film (titanium nitride film) is formed by a sputtering deposition method. Subsequently, a silicon oxide film is formed on the TIN film by a plasma CVD method and patterned into a contact hole shape. Next, a 50 nm-thick TiN film is formed on exposed portions of the TiN film and on the silicon oxide film by a sputtering deposition method. Thereafter, an 800 nm-thick tungsten film is formed on the TiN film by a CVD method.
If any portion of the titanium nitride film covering the titanium film formed on silicon or an aluminum conductive layer is insufficient in thickness, however, the tungsten film may suffer film delamination or react with WF6 to produce volcanoes, unless the heating treatment mentioned in JP2001-168057A or JP11-87272A is performed.
As the result of keen examination, the present inventor has found that if the heating treatment mentioned in JP2001-168057A and JP11-87272A is performed while the titanium film (Ti film) is in contact with a copper conductive layer (Cu film), the state of contact between the Cu film and the Ti film becomes unstable, and therefore, the contact resistance between a conductive plug (a contact conductive plug, a via conductive plug, or the like) including the Ti film as one of the constituent elements thereof and the copper conductive layer increases and varies within a plane of a semiconductor substrate.
If the heating treatment is performed after the formation of the titanium nitride film (TiN film) on the copper conductive layer (Cu film), the barrier properties of the titanium nitride film (TiN film) with respect to Cu degrade, thus causing copper atoms to be liable to diffusion. Consequently, the present inventor has also found that the electromigration (EM) resistance of the bottom of the conductive plug decreases, and the nucleus-forming reaction of the tungsten film (base material of the conductive plug) on a surface of the titanium nitride film (TiN film) becomes unstable, thus leading to the anomalous growth of the tungsten film.